The nation’s largest drugstore chain is telling blood-testing startup Theranos to stop sending samples from its customers to a testing facility that drew regulatory scrutiny over possible patient risks.

Walgreens Boots Alliance Inc. said Thursday that it told Theranos to either send tests to a certified lab in the Phoenix area that Theranos runs or an accredited third-party lab. The decision only affects 40 stores in Arizona and a location in California. Walgreens runs more than 8,000 U.S. locations.

Government inspectors recently warned privately held Theranos that they found several deficiencies at its Newark, California, laboratory, and some “pose immediate jeopardy to patient safety and health.”

Theranos has said the inspection took place last year and doesn’t reflect its current practices. It also says it is taking corrective steps.